<form id="search" name="frm" action="usermanage" method="post">
      <select name="key" >
        <option value="userName">Username</option>
        <option value="fullName">Full Name</option>
        <option value="roleID">Role</option>
    </select>
    <input type="search" name="value" placeholder="Search...">
    <input class="btn_search" type="submit" name="action" value="search">
</form>